1. Field of the Invention
The present invention relates generally to an inspection apparatus, and more particularly to a surface inspection apparatus which can automatically inspect for defects in the surfaces of objects to be inspected as they are carried along on a continuous belt conveyor or the like, by the use of a single optical image sensor or the like.
2. Description of the Prior Art
Recently, many types of devices have been proposed for automatically inspecting objects, as a replacement for the personal inspection conducted by the human eye. In these devices, the appearance or surface of the objects are viewed through optical image sensors such as video cameras or the like to produce video signals thereof and then such video signals are processed in electronic circuitry or the like to automatically determine whether or not a defect in the objects exist.
However, in the above known prior art inspection devices, the video camera is normally fixed and its visual field is limited to one direction. Accordingly, when an object to be inspected is a cubic body such as a cup or the like, its entire round surface cannot be inspected at one time.
Alternatively, methods of inspection have been suggested that use a number of video cameras to view a single object to be inspected so that the inspected object may be simultaneously inspected from several different directions at once. However, this method contains a defect in that it necessitates a number of video cameras as well as multi processing circuits which make the system expensive and which also requires a large inspection space.
Further, proposals have been made to use one video camera and to stop the cubic object, such as a cup at the inspection position, and thereafter rotating the object, so that the inspection area is changed. By thus repeating the inspection several times, the entire round surface of the object will be inspected. This method requires a long time to inspect a single object which makes it impossible to adopt this method to the inspection of a plurality of objects, such as cups or the like, that flow on a belt conveyor.